JSON files have a validation Schema similar to XSD. Most agree it is easier to use and understand. My opinion is that ( with the JSON Schema file) you can have as much control (constraint) or not, over your data validation as you like. A fast overview of the JSON Schema is on YouTube
JSON Schema Overview
That is a overview only. Not all of the options are explained.
There are other videos on YouTube which describe the format and attributes of the Schema format file.
IMNOHO -- The JSON schema is more versatile and powerful than XSD. In fact, a JSON schema is used and required to validate the data interface between the Python API and the C++ API when using the CommandHandler function(s). Graphisoft has said, in the past, that they may move to the JSON format and Schema for other uses in future -- But don't count on it.
Windows 10 - Visual Studio 2019; ArchiCAD 26